In recent years, the development of Intelligent Transport Systems (ITS) has progressed with the aim of achieving smooth automobile travel. As a part of ITS, a driving support system that uses a navigation system installed in an automobile to provide information, warnings, operation support, and so on corresponding to the geographical location of the automobile has been proposed. For example, Patent Document 1 and Patent Document 2 describe systems for controlling a downshift in cases such as when a host vehicle exits a main road of an expressway and moves onto a deceleration lane such as an off-ramp.
In each of the systems described above, an error may occur in a host vehicle position calculated by the navigation system. Therefore, a control subject section is set in advance, and when the host vehicle enters the section, vehicle control is performed. Therefore, driving control may not be executed at an accurate timing, for example deceleration control may be performed before the host vehicle enters the deceleration lane. As a result, the driver may experience an unpleasant sensation, and moreover, smooth travel of other vehicles on the main road may be impaired. Furthermore, if a delay occurs in the timing at which convergence-related driving support is performed during convergence, acceleration prior to the convergence may be insufficient, causing an obstruction to the travel of other vehicles on the main road.
Patent Document 1: Japanese Patent Application Publication No. JP-A-H10-141491
Patent Document 2: Japanese Patent Application Publication No. JP-A-2000-293782